Federal authorities have asked to speak with the wife of the killed Boston Marathon suspect Tamerlan Tsarnaev, her lawyer has said.

Katherine Russell Tsarnaev had not suspected her husband was behind the bombings and had last seen him when she left for work, said the lawyer, Amato DeLuca. She first learned he was a suspect when she saw it on television after the police chase in which he died.

The widow did not speak to federal officials who came on Sunday evening to her parents' home, where she has been staying since her husband was killed during a getaway attempt on Friday.

DeLuca said he spoke with the federal officials but would not offer further details. "We're deciding what we want to do and how we want to approach this," he said.

When asked whether anything seemed amiss to the wife following the bombings, DeLuca said: "Not as far as I know."

DeLuca said his client had not suspected her husband of anything. She had been working 70 to 80 hours, seven days a week as a home healthcare aide. While she was at work her husband cared for their toddler daughter, DeLuca said.

"When this allegedly was going on, she was working, and had been working all week to support her family," he told the Associated Press.

Dzhokhar Tsarnaev, the younger brother, had been off at college and she saw him "not at all" at the apartment they shared with her mother-in-law, DeLuca said.

Katherine Russell Tsarnaev was attending university in Boston when friends introduced her to her future husband at a nightclub, DeLuca said. They dated on and off, then married in 2009 or 2010.

She was raised as a Christian but at some point after meeting Tamerlan Tsarnaev she converted to Islam, he said. When asked why she converted, DeLuca said: "She believes in the tenets of Islam and of the Qur'an. She believes in God."

Tamerlan Tsarnaev, 26, an ethnic Chechen from southern Russia, was believed to be responsible for planting two explosives near the marathon finish line, killing three people and injuring more than 180. His brother, Dzhokhar Tsarnaev, 19, also accused of involvement in the attacks, is in a serious condition in hospital. A motive remains unclear.